#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/select.h>

#define BUF_SIZE 100

int main(int argc, char **argv)
{
    int serv_sock, clnt_sock;
    sockaddr_in serv_adr, clnt_adr;
    timeval timeout;
    fd_set reads, cpy_reads;

    socklen_t adr_sz;
    int fd_max, str_len, fd_num, i;
    char buf[BUF_SIZE];
    if (argc != 2)
    {
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }
    serv_sock = socket(AF_INET, SOCK_STREAM, 0);
    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_adr.sin_port = htons(atoi(argv[1]));

    bind(serv_sock, (sockaddr *)&serv_adr, sizeof(serv_adr));
    listen(serv_sock, 5);

    FD_ZERO(&reads);
    FD_SET(serv_sock, &reads);
    fd_max = serv_sock;
    while (1)
    {
        cpy_reads = reads;
        timeout.tv_sec = 5;
        timeout.tv_usec = 5000;
        fd_num = select(fd_max + 1, &cpy_reads, 0, 0, &timeout);
        if (fd_num == -1)
        {
            break;
        }
        else if (fd_num == 0)
        {
            continue;
        }
        else
        {
            for (i = 0; i < fd_max + 1; i++)
            {
                if (FD_ISSET(i, &cpy_reads))
                {
                    if (i == serv_sock)
                    {
                        adr_sz = sizeof(clnt_adr);
                        clnt_sock = accept(serv_sock, (sockaddr *)&clnt_adr, &adr_sz);
                        FD_SET(clnt_sock, &reads);
                        if (fd_max < clnt_sock)
                        {
                            fd_max = clnt_sock;
                        }
                        printf("客户端到来了，文件描述符是：%d\n", clnt_sock);
                    }
                    else
                    {
                        str_len = read(i, buf, BUF_SIZE);
                        if (str_len == 0)
                        {
                            FD_CLR(i, &reads);
                            close(i);
                            printf("已关闭客户端：%d\n", i);
                        }
                        else
                        {
                            write(i, buf, str_len);
                        }
                    }
                }
            }
        }
    }
    close(serv_sock);
}